Broadband DMS filters in known housings can be matched very well across the entire passband, so that only small changes in the input and output impedance are maintained. Together with the metallic connection areas provided on the chip, known housings form parasitic static capacitances that can reach considerable values. Therefore, external inductors are typically used in these housings in order to equalize the effects of the parasitic static capacitances.
Currently, housings with significantly smaller sizes and improved materials are being developed. Also, bare-die applications are undergoing development in which the bare chip is soldered onto a substrate. Wafer level packages that use, for example, a glass carrier with significantly lower permittivity than a standard ceramic carrier can also significantly lower the value of the static capacitances.
During the development process of such new designs, it has emerged that matching by means of the simple re-dimensioning of external inductors already in use is no longer possible for components made from the latest developments with reduced static capacitances. The margin of deviation that can be achieved in this way for the admittance on the input and output remains too large.